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Feb. 4, 2011 -- Should Green Bay Packers quarterback Aaron Rodgers have stayed in a crucial playoff game after taking a violent blow to the head?

A Super Bowl berth was the ultimate outcome. But had Rodgers taken a new one-minute concussion test on the sidelines, his coaches would have known whether he was at risk of a far worse outcome: serious brain damage.

The test is simple. Before the game, a coach or trainer shows each athlete a set of three index cards. Each card has a series of numbers scattered across eight lines. The athlete reads the numbers from left to right.

After a blow to the head, the athlete goes to the sidelines and retakes the test. If he's five seconds slower, he may have suffered a concussion -- and is at serious risk if his head gets hit again.

It sounds too simple to be true, especially because only the most sophisticated brain scans can detect many concussion effects.

But it turns out that eye movement is strongly linked to neurological function. The simple test, called the King-Devick or K-D test, shows whether eye movement is impaired. If so, it's likely that the athlete has suffered a concussion.

Concussion Test ID's Brain Damage Risk

A single, first-time concussion often heals without incident. But before it heals, it makes a person extremely vulnerable to brain damage from a second head trauma.

About 17% of boxers, for example, develop a form of dementia called chronic traumatic encephalopathy (CTE). CTE also affects athletes in other contact sports such as football, soccer, and hockey. Symptoms, which can be disabling, include chronic headaches, fatigue, sleep difficulties, sensitivity to light and noise, dizziness, and short-term memory loss.

"Concussion is a complex type of brain injury that is not visible on the routine scans we do of the brain, yet is detectable when we measure important aspects of brain function, such as vision," study researcher Kristin Galetta of the University of Pennsylvania says in a news release.

"If validated in future studies, this test has the potential to become a standard sideline test for athletes," senior study researcher Laura Balcer, MD, says in the news release.

Galetta, Balcer, and colleagues tried out the test on 27 boxers and 12 mixed-martial-arts fighters. All took the K-D test before and after a sparring bout (boxers) or a match (MMA fighters). A doctor with experience in both sports rated each participant for blows taken to the head.

Boxers and fighters who did not suffer head trauma actually did a little better on the second test than on the first. But those who took serious blows to the head did worse. A cutoff time of 5 seconds worse on the second test identified athletes who failed more intensive testing for concussion.

The test does not definitively diagnose concussion. But last November, the American Academy of Neurology called for any athlete suspected of having a concussion to be pulled from a game.

Because the concussion test takes less than two minutes, it could be done during a single football game time out. But will it really work in an actual game?

The Penn Quakers football team, men's and women's soccer teams, and men's and women's basketball teams are trying it out. Results won't be ready for this year's Super Bowl, but maybe next year Rodgers' coaches will feel a little bit less anxious about sending him back into the game if he takes a hit to the head.

The Galetta study appears in the April 26 issue of the journal Neurology.